Inhibition of breast tumor growth by N(G)-nitro-l-arginine methyl ester (l-NAME) is accompanied by activation of fibroblasts

The impact of nitric oxide on HER family post-translational modification and downstream signaling in cancer

The human epidermal growth factor receptor (HER) family consists of four members, activated by two families of ligands. They are known for mediating cell-cell interactions in organogenesis, and their deregulation has been associated with various cancers, including breast and esophageal cancers. In particular, aberrant epidermal growth factor receptor (EGFR) and HER2 signaling drive disease progression and result in poorer patient outcomes. Nitric oxide (NO) has been proposed as an alternative activator of the HER family and may play a role in this aberrant activation due to its ability to induce s-nitrosation and phosphorylation of the EGFR. This review discusses the potential impact of NO on HER family activation and downstream signaling, along with its role in the efficacy of therapeutics targeting the family.

Anti-cancer effect of in vivo inhibition of nitric oxide synthase in a rat model of breast cancer

Increased expression of nitric oxide synthase (NOS) is associated with different cancers such as cervical, breast, lung, brain, and spinal cord. Inhibition of NOS activity has been suggested as potential tool to prevent breast cancer. The anti-tumor therapeutic effect of L-nitro arginine methyl ester (L-NAME), NOS inhibitor, using in vivo models is currently under investigation. We hypothesized that L-NAME will show an anti-tumor effect by delaying a progression of breast cancer via a modulation of cell death and proliferation, and angiogenesis. We used a novel model of anti-cancer treatment by the administration of L-NAME (30 mg/kg in a day, intraperitoneal) injected every third day for five weeks to rat model of 7,12-dimethylbenz[a]anthracene (DMBA)-induced breast tumor. Concentrations of nitrite anions, polyamines, malondialdehyde, NH₄⁺ levels, and arginase activity in the blood were decreased in DMBA + L-NAME-treated rats compared with DMBA rats. The mortality rates, tumor number, weight, and volume, as well as the histopathological grade of breast cancer were also significantly reduced. In addition, L-NAME treatment showed a delay in tumor formation, and in body weight compared with rats administrated only with DMBA. In conclusion, our data show that L-NAME is a promising anti-cancer agent to treat breast cancer, which can lead to development of anti-tumor therapeutic tools in future.

S-Nitrosylation in Tumor Microenvironment

S-nitrosylation is a selective and reversible post-translational modification of protein thiols by nitric oxide (NO), which is a bioactive signaling molecule, to exert a variety of effects. These effects include the modulation of protein conformation, activity, stability, and protein-protein interactions. S-nitrosylation plays a central role in propagating NO signals within a cell, tissue, and tissue microenvironment, as the nitrosyl moiety can rapidly be transferred from one protein to another upon contact. This modification has also been reported to confer either tumor-suppressing or tumor-promoting effects and is portrayed as a process involved in every stage of cancer progression. In particular, S-nitrosylation has recently been found as an essential regulator of the tumor microenvironment (TME), the environment around a tumor governing the disease pathogenesis. This review aims to outline the effects of S-nitrosylation on different resident cells in the TME and the diverse outcomes in a context-dependent manner. Furthermore, we will discuss the therapeutic potentials of modulating S-nitrosylation levels in tumors.

Exploiting S-nitrosylation for cancer therapy: facts and perspectives

S-nitrosylation, the post-translational modification of cysteines by nitric oxide, has been implicated in several cellular processes and tissue homeostasis. As a result, alterations in the mechanisms controlling the levels of S-nitrosylated proteins have been found in pathological states. In the last few years, a role in cancer has been proposed, supported by the evidence that various oncoproteins undergo gain- or loss-of-function modifications upon S-nitrosylation. Here, we aim at providing insight into the current knowledge about the role of S-nitrosylation in different aspects of cancer biology and report the main anticancer strategies based on: (i) reducing S-nitrosylation-mediated oncogenic effects, (ii) boosting S-nitrosylation to stimulate cell death, (iii) exploiting S-nitrosylation through synthetic lethality.

Relevance of iNOS expression in tumor growth and maintenance of cancer stem cells in a bladder cancer model

The expression of inducible nitric oxide (NO) synthase (iNOS) in human bladder cancer (BC) is a poor prognostic factor associated with invasion and tumor recurrence. Here, we evaluated the relevance of iNOS expression in BC progression and in cancer stem cell (CSC) maintenance in a murine BC model. Also, iNOS expression and CSC markers were analyzed in human BC samples. iNOS inhibitors (L-NAME or 1400W) or shRNA were used on murine BC model with different iNOS expressions and invasiveness grades: MB49 (iNOS+, non-muscle invasive (NMI)) and MB49-I (iNOS++, muscle invasive (MI)), in order to analyzed cell proliferation, tumor growth, angiogenesis, number of CSC, and pluripotential marker expression. iNOS, SOX2, Oct4, and Nanog expressions were also analyzed in human BC samples by qPCR and immunohistochemistry. iNOS inhibtion reduced parameters associated with tumor progression and reduced the number of CSC, wich resulted higher in MB49-I than in MB49, in concordance with the higher expression of SOX2, Oct4, and Nanog. The expression of SOX2 was notoriously diminished, when iNOS was inhibited only in the MI cell line. Similar results were observed in human samples, where MI tumors expressed higher levels of iNOS and pluripotential genes, in comparison to NMI tumors with a positive correlation between those and iNOS, suggesting that iNOS expression is associated with CSC. iNOS plays an important role in BC progression and CSC maintenance. Its inhibition could be a potential therapeutic target to eradicate CSC, responsible for tumor recurrences. KEY MESSAGES: • iNOS expression is involved in bladder tumor development, growth, and angiogenesis. • iNOS expression is involved in bladder cancer stem cell generation and maintenance, playing an important role regulating their self-renewal capacity, especially in muscle invasive murine bladder cancer cells. • iNOS expression is higher in human muscle invasive tumors, in association with a high expression of pluripotential genes, especially of SOX2.

Real-Time Imaging and Simultaneous Quantification of Mitochondrial H2O2 and ATP in Neurons with a Single Two-Photon Fluorescence-Lifetime-Based Probe

Mitochondrial oxidative stress and energy metabolism are vital biological events and are involved in various physiological and pathological processes such as apoptosis and necrosis. However, it remains unclear how the dynamic patterns of mitochondrial hydrogen peroxide (H₂O₂) and adenosine-5'-triphosphate (ATP) change in these events and, more importantly, how they affect each other. Herein, we developed a single two-photon fluorescence-lifetime-based probe (TFP), which offered real-time imaging and the simultaneous determination of mitochondrial H₂O₂ and ATP changes in two well-separated fluorescence channels without spectral crosstalk. The fluorescence lifetime of TFP exhibited good responses and selectivity in the detection ranges of 0.4-10 μM H₂O₂ and 0.5-15 mM ATP, taking advantage of accuracy and the quantitative ability of fluorescence lifetime imaging. Using this useful probe, we studied the relationship between H₂O₂ and ATP in mitochondria and visualized the dynamic level changes of mitochondrial H₂O₂ and ATP induced by the superoxide anion (O₂^•-). It was discovered that O₂^•- stimulation in a short period of time (8 min) temporarily changes the levels of H₂O₂ and ATP in mitochondria, and neurons were capable of recovering to the initial state in a short time. However, increasing time of up to 50 min of O₂^•- stimulation led to permanent oxidative damage and an energy deficiency. Meanwhile, it was first found that the exogenous stimulation of O₂^•- and H₂O₂ had different impacts on the levels of mitochondrial H₂O₂ and ATP, in which O₂^•- demonstrated more severe and negative consequences. As a matter of fact, this work not only has provided a general molecular design methodology for multiple species imaging but also has revealed oxidative-stress-induced intracellular functions related to H₂O₂ and ATP in mitochondria based on this developed TFP probe.